Hi Bret,Here are my hand trimmed T foils,i used to run on my boat, a sail boat is a great way to play with foils .Keeping hand trimmed is a big problem,becous of raped speed change,i found it hard to make a neutral running foil,i started to play with water level trimmed foils,some of the advantages of foils are not always obvious.I am amazed at how running a foil (not lifting)under my boat damped out reflective chop,and boat wakes ,the faster you go the more the damping effect to a point.When other boats are bobbing crazely i slice through the water rock steady.All though one time when i was going at warp speed,the foil suddenly lifted onto the surface of the chop and barrel rolled me.I use my boat less for foil work now, its just less trouble to get a board than a boat over the sand into the water.

Nice work with the foils Chris, I also did some foiling with the modern Laser class. Amazingly better on foils than the old boat but the twin foils are a devil to balance, it's the most defining moment I had in foil design where I'd laboured for years following sail boat foil design, following aeroplane wing design, following power boat foil design and failing miserably. Despite following everyone before me, I was failing but doing my best.
Until I chose to go in a different direction and change to a single foil that ran front to back. Of course it had to be wide but I add the width of the two lateral foils and ......it works better than any lateral foil setup. Chris , your foils kinda are similar to mine where you foils are wide but have a long chord which create pitch stability.

Taking a look at foil design, a flat horizontal foil seems to be the most efficient and stable shape. A foil that's wider is more stable in the direction, a foil that's longer front to back is more stable in that plane. Riding a foil flat, straight and without turning is OK, but in order to make foiling in the surf more enjoyable the design needs to incorporate features that will make it reliable and manouverable.

If you tilt the foil as you turn it loses that premium of balanced lift. But you can alter the design to maintain lift throughout turns.

Now with a flat foil when you turn, a lot more of your weight is now on one side of the foil.

image.jpg (3.93 KiB) Viewed 2159 times

If the foil has an Anhedral or downward tip then it already returns less than perfect lift but when you turn the tip angle will have a greater downward angle. Here's my lateral Spitfire Anhedral foils...

image.jpg (24.23 KiB) Viewed 2159 times

Initially the anhedral tip makes it easier to start the turn but loses lift too. When the board and foil are tilted at a large angle it does provide some real grip but that angle is around 70+ degrees so it's almost vertical like a fin.
On the other hand a Dihedral tip is turned up. Initially it also returns less lift than a flat foil.

But as you turn and tilt a foil with Dihedral tips, the centre area moves away from horizontal but the tip becomes more horizontal and so add lift on the inside of the turn.

Hi Brett,I thought we were not on the same page with this foil thing for a time,but now realize both the foil types you are talking about are on my boards but packaged diferantly ,i have the wing foil under the front to back foil witch is the tail rail.The wing foil is the pitch pivot,but plaining on top of the water with the wing foil seams under estemated , i am useing the foils as leverage in the steep sections ,and then on top when cutting back and running flat sections ,that is why i am going for triangle foils on the next board to get a larger plaining area ,with about the same amount of wing in the steep sections.

Hi Brett,
I have started the SR-72 project.Here are some pics,this part takes the longest agonizing over were to place the foil,and angel of incidenc.my other boards have about 3deg positive angle,i think this will have 0.What angle do you use

Hi Chris, I use 0 degrees because then the hull of the board and the foil are parallel. So water can flow between both surfaces without being blocked or trapped. If you're paddling and the board is at the optimum angle for speed, so should the foil so it's neither digging of pushing water. I have tried lots of angles and with the old lateral foils they were set at different angles but 0 degrees makes sense and it's easy.
I can see the SR.-70 influence in your foil straight away !
It's exciting to watch someone else build a foilboard, Dave T shows his build pics too and it's always amazing how other people create things with their skills.

Hi Brett,
The torsion box has been glue in,and i am close to the finel cut on the board. this board will be very thin with hard rails,i am trying to keep the foil as light as posible ,with foam box beams ,its a new method to me!! but thats how we grow.

Chris, that board is looking fantastic ! Are you using CSM, and / or vac bagging ?
It looks like you're a metal worker but your boards always look really professionally finished.
Are you foiling your foils or leaving them as a flat plate ?

Hi Brett,
I am no sure what CMS is ,but it is all hand layup on XPS with brushes and rollers,mostly 6 oz cloth .I like useing ridges and concave sections to strengthen , the tip half of the foil will have a laminar- flow section blending to the flat center

CSM - chop strand mat, is like shredded wheat fibreglass, used a lot in boating
Your description of your foil sounds cool. Can't wait to check it out !!
Here's my project with 10 degrees of Anhedral, only 3 mm ply but I'll vac bag a few layers of 6 oz on both sides and then sand it down. I'm keeping it minimal displacement, minimal form drag, minimal weight. I see the foil as a finely honed blade slicing thru the maelstrom of the wave.
The Delta shape makes sense to me because when you turn you're lifting the nose and putting more weight towards the back, especially when you're riding a shortboard foil. It's the same weight shift as when you're on a traditional shortboard.

and put all that in a plastic bag with a tube that connects to the pump.

The pump sucks the air out of the bag but it also sucks the plastic and the glass on to the ply and draws away excess resin so you end up with a glass job that sticks exactly to the shape and doesn't carry excess resin that makes it heavier than it needs to be. You only throw away a plastic bag and a bit of sticky tape and there's no resin to clean up or scrape off the floor like standard laminations.

A few hours later it comes out of the bag and it's done, But epoxy resin needs a few days to harden to its maximum.
In one shot you can glass both sides of anything and get a quality item with little skill, thankfully.
I still need to trim around the edges, maybe add a bit of artwork and then it's ready to ride.

Hi Brett this May seem like a silly question but how do you stop the plastic bag from sticking to the wet glass?
I have very limited glassing experience but very keen to experiment with some shapes so vacuuming May be a option.
Thanks for the info you have shared.

Hi guys, Chris, the plastic bag is polyethylene, it's very cheap stuff, I'm using 240 litre OTTO bin liners, the plastic crinkles when you scrunch it and it just doesn't stick to resin at all, never. They're about 50c each. The other type of plastic garbage bag is polyester which doesn't work.
I'm happy to give you all the info so you can do it yourself, it's so easy I haven't hand laminated a board for 5 years and you can do veneer and multiple layers. I'll show you more in this thread.
I too stand around for hours looking at the board and also drawings I've done, I do a lot of drawing in my head and working out how the water will flow around it.
Initially I used to think about whether it will lift but after one wave lifting isn't an issue. It's trying to harness the lift so it's controllable.
The lift Quadrouples as the speed doubles and I know that a foil around 225 sq inches lifts my 80 kg at 4 kph (walking speed) so my first foils lifted easily on very small waves. But when I tried them on waves about 3 ft high at the face the foils were leaping out of the water. Current understanding of foils said that they lose efficiency when they get within a chord depth to the surface but that's wrong when you're in the surf. Foiling in the surf has its own theories to be discovered. It's a pity there aren't more people around the world doing this but it's also fantastic because we are real explorers, 7 Billion people on earth and there's only 3 of us making our own foil boards and discoveries. That is cool.

Sadly Terry isn't with us anymore, however if there's a chance of honouring his knowledge and openness to share, I think we should do it. Terry may not have been the first to foil but he was the first to build his own from original theory and completely understand why it works.

Hi Brett,
It is very interesting all the different ideas out there,it can be difficult to be certain all this complexity is improving riding a wave,we all have differnt goals on a wave.My improvement goals is to be the board that rides the longest on any wave on any day.Like on a close out day i want to double the distance a body board can go along the face.My new foil is going to be very interesting with all the extra lift area.